Shrinkproofing wool by acidification and subsequent application of alkali metal bromates and halide



United States Patent ()flfice 3,128,145 Patented Apr. 7., 1964 SHRINKPRUOFING WOOL BY ACIDIFICATIUN AND SUBSEQUENT APPLICATIGN F ALKALI METAL BROMATES AND HALKDE John P. Redston, Upper Montclair, NJ., Malcolm 3. Reider, Reading, Pa., and Gerard M. Weiss, White Meadow Lake, Ni, assignors to Drew Chemical Corporation, a corporation of Delaware No Drawing. Filed Aug. 9, 1961, Ser. No. 130,264

7 Claims. (Cl. 8128) The present invention is directed to the shrinkproofing of wool, and more particularly to the treatment thereof with bromate/ halide salt solutions. In copending application Serial No. 41,760, filed July 11, 1960, now Patent No. 3,098, 694, such a process is described and the present process is an improvement thereon. The details as set forth therein are applicable to the present invention.

In the prior art, there was a process in which the wool was immersed in a bath of alkali metal bromate and chloride together with a strong acid. The wool was allowed to remain therein for a substantial length of time until the bromate ion disappeared. In another prior process the wool was immersed in water and a bromate and bromide solution introduced. Then a solution of acid and water was added over a period of time. The prior art suffers from several deficiencies among which are the following:

(1) In the prior art a relatively long time was necessary for proper shrinkproofing of the wool because of the slow reaction of the chemicals. This process did not lend itself to a continuous method of fabric processing, which is a necessity to modern industrial requirements.

(2) If the reaction was accelerated, halogen gas would be evolved faster than it could be absorbed by the wool and it would constitute a loss and a hazard.

(3) The prior art was limited exclusively to batch processes.

(4) The methods described in the prior art were relatively costly.

(5) Difficulties in subsequent dyeing and finishing were often the result of practicing the prior art.

(6) In the prior art the weight of the solution, in which the chemicals are reacted with the wool, was usually twenty to fifty or more times the weight of the wool. It is also among the objects of the invention to reduce the amount of chemicals necessary in the operation and wherein the weight of the solution in which the chemicals are reacted with the wool is usually less than the weight of the dry wool.

The present invention is intended and adapted to overcome the'defects in prior processes, it being among the objects thereof to provide a continuous and low cost operation and in which the reaction is rapid, even, and complete.

It is further among the objects of the invention to provide a process which will provide uniform shrinkage of the wool, and result in a product which permits level dyeing and the wool to retain its original feel or hand.

The present process is essentially continuous and does not require that the wool be immersed in or passed through a bath of the substances with which it is treated. It is a rapid treatment with a uniform result. The following are specific examples of the operation of the invention:

Example 1 W001 fabric oiled with suitable and easily removable oils is impregnated with sulfuric acid of usual and suflicient strength so that 5-10% acid is taken up by the fabric. The fabric is squeezed and dried and then heated to high temperatures to carbonize all the vegetable matter.

The fabric is then fulled using nonionic detergents and cationic materials and subsequently washed in a dolly or continuous washer. During this wash, the emulsified oils, dirt, etc., will be removed and some acid will remain on the cloth. (Actually this process of acid fulling after carbonizing in the grease is covered by US. Patent 2,806,804, granted to Davis and Redston.) It is then necessary to add enough acid so that 410% acid is on the fabric. This may be done by addition of acid to the dolly washer or by having the fabric pass through an acid solution in the last bowl of the continuous washer.

After washing, the fabric is processed over a scutcher or opening device to take out any twists in the fabric, and it is then passed through heavy squeeze rolls. After squeezing the fabric to about 50-60% of its own weight of water, the sulfuric acid is evenly distributed through and combined with the wool as a result of acid migration in fulling and securing.

The open width fabric is now evenly sprayed with a solution of potassium bromate and the bromide or chloride salt of an alkaline metal, such as sodium or potassium, containing a wetting agent, in such an amount, that deposits say 10100% of solution based on the weight of the wool fabric, 30-50% being a preferable amount. The solution may be sprayed on to one side or both sides of the fabric after which it is immediately passed between roll at sufiieient pressure to cause the new solution to become pressed into the interior of the fabric. The chemicals are allowed to react on the fiber for up to 5 minutes and the fabric is then rinsed (neutralized if desired), treated with alkali metal thiosulfate as an antihalogen treatment, rinsed and dyed.

Such dyeings, even with difficult milling colors, are perfectly level. The hand or feel of the fabric is identical to that of the Wool before treatment. There is no undue increase in alkali solubility, as a measure of chemical damage, and the fabric maintains its strength and other desirable properties.

Example 2 An alternative method of applying the treatment to the evenly acidified cloth is to use an exceptionally low volume padder, either horizontal or vertical, which is exhausted of bromate/halide solution as soon as the piece passes through, the low volume padder being continually replenished with a fresh solution of bromate/halide from a reservoir.

Example 3 A further extension of the continuous process is found for those fabrics that do not require carbonizing by the following technique:

The fabric, direct from the loom is scoured in a continuous washer or in a dolly washer, and it is then fulled using by weight of a 710% solution of sulfuric acid plus nonionic detergent and cationic agent or other fulling agents. Thereafter, the fabric is straightenend out on the scutoher, run through squeeze rolls to leave at least 4.5% sulfuric acid on the fiber and sprayed or shallow padded with the bromate/halide solution without the use of any further wetting agent beyond that which is still present in the cloth from the fulling operation.

Example 4 The present process also covers a further embodiment where the fabric is fulled and scoured, preferably but not necessarily under acid conditions, and is then padded through an acid solution of 310% strength, dried and carbonized in the normal manner well known to those versed in the art. It is then passed through the crusher as usual to remove the carbonized vegetable matter. At this stage the acid is evenly impregnated across the dry cloth. The dry fabric at open width is now sprayed with bromate/halide solution and wetting agent as described previously, or padded with a continually fresh or replenished solution of bromate/halide solution plus a wetting agent or the bromate/halide salt solution plus wetting agents may be applied by means of a transfer roll by which means the dry acidified fabric passes between two rolls of a horizontal padder, the bottom roll being covered with a suitable absorbent material such as cotton cloth, which is partially immersed and running in the shrinkproofing solution, so that the reaction takes place on the fabric itself rather than in a bath as in the previous art. The fabric is neutralized with an alkali, given an anti-halogen treatment and treated as above, rinsed and dyed.

In all these examples the reaction time is very rapid, usually under 2 minutes, which with the quick neutralizing, anti/halogen treatment, etc., lends itself to modern methods of continuous processing. A number of advantages are inherent in the invention. It may be applied to all those processes where wool in the normal procedure of manufacture is impregnated with an amount of sulfuric acid approximately equal to 410% of its weight of sulfuric acid, such examples are the continuous scouring of raw wool followed by impregnation with sulfuric acid, drying, carbonizing and crushing. At this stage before the normal neutraliZing, the wool may be impregnated with the bromate/halide solution for the shrinkproofing to take place in situ as explained above.

Heavy papermakers woven felts may be acid fulled and rinsed, or scoured and acid fulled and hydro-extracted and/or dried. As they revolve lengthwise on a suitable open roller they may be sprayed from both sides of a low pickup and given the shrinkproofing process. The same spray equipment is then used for neutralization antihalogen or other treatments.

It has been found that it is highly desirable to carefully regulate the wet-out of dry fabric. The wetting time will vary with each cloth and will also depend on the equipment being used. When a transfer roll is used, it is necessary to have instantaneous wet-out, but when a pad liquor is used, the fabric should wet-out in such a manner that the liquor flows only into the fabric. This allows the whole fabric to become thoroughly and evenly wet with the bromate/halide solution before the release of the halogen takes place in the interstices of the fabric or on or in the individual fibers rather than in the liquor.

The amount of sulfuric acid present on the dry fabric should be about 2% to and preferably about 6%, but the bromate and common salt can be varied between wide limits. Low amounts of bromate require high amounts of common salt. Conversely, higher amounts of bromate require less amounts of common salt; these can be varied between these limits:

Percent Bromate 0.5-1.5 Common salt 26-12 all these amounts being on the weight of the wool.

The mechanism of the process seems to be that the bromate oxidizes the common salt to release chlorine. The process is one of halogenation, chlorine and some bromine being released. When larger amounts of common salt are used, the halogen released is entirely taken up by the wool. However, the process has a large safety factor and while the lowest amount of bromate is used for reasons of economy, nevertheless amounts as high as 3% bromate and 12% common salt may be used without damage to the wool.

Furthermore, the process appears to affect the directional frictional properties of the wool fiber in such a way that an increase in strength of wool fabrics is the result. The percentage increase in strength is substantial, being in the order of 25%, but varying widely depending on the construction of the yarn and fabric. Increases as high as 50% have been recorded.

A most interesting and perhaps unique part of this process is that the dry fabric containing about 5% to 7% sulfuric acid may be run through a horizontal padder, with the bottom roller running in the bromate/ halide salt solution plus wetting agent, in such a manner that no sulfuric is leached out of the fabric so that it is transferred to the bromate/halide salt solution in the padder to release halogen gas. Even after a long run of pieces the pH of the bromate/halide only drops from pH 5.5 to pH 4.5 and this may be arrested by the addition of a buffer salt such as sodium acetate. The pressure on the roll is such that the wet pickup of solution from the padder is about 60% plus or minus 20% on the weight of the dry fabric. In this manner the deposition of the bromate/ halide salt solution is as evenly distributed across the piece as was the original pickup of sulfuric acid at the carbonizer. Due to the relatively low pickup of wet solution, there is no migration of bromate/halide salt solution on the fabric and the treatment takes place evenly across the fabric and even dyeing is the result.

While the halide used is generally sodium chloride, other alkaline metal chlorides, such as potassium or calcium or the like, may be used. The strength of the aqueous solution of halide and bromate may vary considerably, but a relatively concentrated solution is usually applied to the wool, say about 2% water solution of the bromate and 7% of the halide. Where sodium chloride is used, the concentration may be about 12%. The liquor applied to the wool is usually about equal to the weight of the wool, and can profitably be even less than a 1:1 ratio.

What is claimed is:

l. A method of shrinkproofing wool which comprises first treating said wool with aqueous sulfuric acid, then pressing said wool and removing excess water therefrom, the amount of sulfuric acid remaining on the wool after pressing being about 2%10% by weight, thereafter depositing on and thereby wetting the wool with an aqueous solution of alkali metal bromate and alkali metal halide so that substantially all of the acid remains on the wool, said halide being taken from the class consisting of chloride and bromide, the amount of bromate so deposited being about 0.5%-1.5% and the halide being about 26%- 12% based on the weight of the wool, the higher amounts of bromate corresponding to the lower amounts of halide,

maintaining contact of the wool with the salts for a period not over about two minutes to substantially completely decompose the bromate, and subsequently neutralizing the acid.

2. A method according to claim 1 characterized in that said wool is dried prior to said wetting.

3. A method according to claim 1 characterized in that said solution is sprayed substantially uniformly on said wool.

4. A method according to claim 1 characterized in that said wool is treated with a soluble thiosulfate after the neutralization thereof.

5. A method according to claim 1 characterized in that the amount of acid on said wool is about 5-7% by weight.

6. A method according to claim 1 characterized in that said wool is substantially continuously moved to the acid treatment and then to the bromate/ halide treatment.

7. A method according to claim 1 characterized in that a reaction between the bromate/halide solution and the acid is caused to take place on the wool, the latter being out of any bath.

References Cited in the file of this patent UNITED STATES PATENTS 2,508,007 Bloch et al May 16, 1950 2,702,737 Koons Feb. 22, 1955 2,714,051 Barnes July 26, 1955 2,923,596 Levin Feb. 6, 1960 

1. A METHOD OF SHRINKPROOFING WOOL WHICH COMPRISES FIRST TREATING SAID WOOL WITH AQUEOUS SULFURIC ACID, THEN PRESSING SAID WOOL AND REMOVING EXCESS WATER THEREFROM, THE AMOUNT OF SULFURIC ACID REMAINING ON THE WOOL AFTER PRESSING BEING ABOUT 2%-10% BY WEIGHT, THEREAFTER DEPOSITING ON AND THEREBY WETTING THE WOOL WITH AN AQUEOUS SOLUTION OF ALKALI METAL BROMATE AND ALKALI METAL HALIDE SO THAT SUBSTANTIALLY ALL OF THE ACID REMAINS ON THE WOOL, SAID HALIDE BEING TAKEN FROM THE CLASS CONSISTING OF CHLORIDE AND BROMIDE, THE AMOUNT OF BROMATE SO DEPOSITED BEING ABOUT 0.5%-1.5% AND THE HALIDE BEING ABOUT 26%12% BASED ON THE WEIGHT OF THE WOOL, THE HIGHER AMOUNTS OF BROMATE CORRESPONDING TO THE LOWER AMOUNTS OF HALIDE, MAINTAINING CONTACT OF THE WOOL WITH THE SALTS FOR A PERIOD NOT OVER ABOUT TWO MINUTES TO SUBSTANTIALLY COMPLETELY DECOMPOSE THE BROMATE, AND SUBSEQUENTLY NEUTRALIZING THE ACID. 